The invention relates to a compressor, particularly in an exhaust gas turbocharger, for an internal combustion engine with a compressor wheel rotatably supported in a compressor housing and a diffuser which is arranged in the compressor housing upstream of the compressor wheel and has a variable diffuser geometry formed by adjustable guide vanes.
In such a compressor as described for example in U.S. Pat. No. 5,207,559, fresh air is supplied to the compressor by way of a compressor supply channel and is compressed by a compressor wheel in the compressor housing and is then conducted downstream of the compressor wheel through a diffuser. The compressor wheel is driven via a shaft by a turbine with a turbine wheel to which gas under pressure is supplied.
In order to increase the operating range of the compressor which is limited on one hand in the area of small mass flows by the pumping limit and, on the other hand, in the area of large mass flows by the blocking limit, the compressor has a variably adjustable diffuser geometry which permits to change the geometry of the diffuser downstream of the compressor wheel depending on the momentary operating point of the compressor. The diffuser geometry comprises guide vanes which are distributed over the circumference of the diffuser and are pivotally supported so as to be adjustable and a rotatable adjustment ring is provided with adjustment members engaging the guide vanes for pivoting the guide vanes about their pivot axes so as to adapt the guide vane positions to various flow conditions in the diffuser.
The adjustment movement of the adjustment ring is transferred by the adjustment members to the guide vanes which are supported in the housing. The adjustment members are rotatably supported by the adjustment ring and bridge a radial gap between the adjustment ring and the guide vane pivot shafts. Because of the pivotal support of the guide vanes shafts in the housing and the distance between the guide vane shafts and the support shafts of the adjustment members, the adjustment ring can be pivoted only to a limited degree. Large adjustment movements cannot be accomplished with this adjustment arrangement and an accurate adjustment of the guide vane positions cannot be ensured.
It is the object of the present invention to provide such a compressor with a variably adjustable diffuser geometry which is simple in design and accurately adjustable. It should also be safe from jamming and from distortions and operable with relatively small adjustment forces.